This invention is concerned with computerized tomographic (CT) systems, and more particularly with such systems equipped with multiple sources of radiation mounted for rotation around the patient at different locations along the longitudinal axis of the patient or object, and further wherein the X-ray beams from each of the sources encompass multiple rows of detectors.
The first CT scanners used sources transmitting X-rays with pencil beams and oppositely disposed single detectors which were moved laterally and then rotationally relative to the object. The CT scanners evolved into using X-ray sources transmitting rotatable fan beams along with an oppositely disposed rotatable detector array. In those first rotate-rotate CT scanners, a single row of detectors was used in the detector array. The fan beam angle was sufficiently large so that the fan beam encompassed the single row of detectors. The length of the detectors along the patient or object axis (the Z axis) defined the maximum slice width that could be covered in a xe2x80x9csingle-shotxe2x80x9d without the scanned object or the scanning frame (hereafter referred to as a xe2x80x9cscanning unitxe2x80x9d) being moved during the scan. In the early ""90s, a dual slice machine was introduced in which the oppositely disposed detector array, comprised at least two rows of detectors. This increased the coverage in the Z direction. See, for example, U.S. Pat. No. 5,228,069, the contents of which are incorporated herein by reference and made a part hereof.
Another improvement in the scanners was the use of multiple focal spots in the X-ray source, which substantially increased the resolution of the acquired images. See, for example, U.S. Pat. No. 4,637,040, the contents of which are incorporated herein by reference and made a part hereof. Subsequently, multiple X-ray sources at the same Z location were used with detector arrays capable of detecting X-rays from more than one slice. Thus, the detectors were arrays of multiple rows of detectors, so that in a single revolution data for multiple slices were acquired. See, for example, U.S. Pat. No. 5,966,422, the contents of which are incorporated herein by reference and made a part hereof. A further improvement was the provision of helical scans. See, for example, U.S. patent application Ser. No. 08/556,824 and French Patent 9209141, the contents of each of which are hereby incorporated herein by reference.
However, until the present invention, there has been no known CT scanner that combines multiple X-ray sources and associated detector array units wherein the units are displaced relative to each other along the Z axis, and wherein each of the arrangements are capable of acquiring multiple slice data.
Besides other advantages, some embodiments that use multiple source detector array arrangements displaced along the Z axis in combination with detector arrays that comprise multiple rows of detectors or large area detectors can provide one or more of the following: large area coverage, high quality time-coherent CT scans, minimize potential cone-beam artifacts, decreases the technical complexities involved in fast data extraction, which are needed for simultaneous imaging of high-resolution volumes of interest (VOI) in the scanned objects. Such combinations of X-ray sources and detector array combinations can provide high-resolution images of complete, large organs such as, for example, the heart in a time-coherent xe2x80x9csingle shotxe2x80x9d image without the need to move the patient or the scanning frame, in order to scan different regions of the volume of interest. This enables a simultaneous scan, or a true cine scan via either xe2x80x9ccontinuous-dynamicxe2x80x9d or xe2x80x9cgatedxe2x80x9d axial scans. In cases where a coverage larger than the basic single shot is needed, either a series of axials, or a contiguous helix scan can be done, still accelerating the speed and improving the quality of a single-source system, with a single detector array, having the same or a smaller coverage.
According to an aspect of some embodiments disclosed herein, there is provided a plurality of radiation sources, each source operating with a detector array to form a scanning unit wherein the scanning units are shifted with respect to each other along the longitudinal axis of the object. Optionally, either the distance between arrays or cooperating baffles are designed so that each of the fan beams covers a different object plane or volume. Object planes or volumes may be contiguous.
In accordance with some embodiments of the present invention, a unique CT scanner system is provided. The system comprises a plurality of X-ray sources mounted around the patient at different Z (axial) locations with detector arrays displaced opposite to each of the sources at the different Z locations. Each of the X-ray beams encompasses multiple rows or large area arrays of detectors to form scanning units, so that a rotation around the scanned object (patient or any other object) may provide simultaneous multi-slice image data. In this manner, the scanning units, i.e., the multiple X-ray sources and oppositely disposed large area detectors or multiple rows of detectors, enable time-coherent coverage of a large volume of an object. Such coverage has never before been accomplished. Thus, time-coherent multiple slice or large volume coverage by the detector arrays can be made in a single rotation of the unique CT scanning units, i.e., the multiple sources combine with individual oppositely disposed unique detector array arrangements capable of being displaced from each other in the Z direction.
There is thus provided, in accordance with an embodiment of the present invention, a CT system is provided; the CT system includes a plurality of X-ray sources mounted on a gantry for rotation about an object, said X-ray sources being located at different axial locations, X-ray detector arrays mounted on said gantry individually associated with and situated opposite to each of said X-ray sources at the different axial locations and each of said detector arrays having multiple rows of detectors in the axial direction, said multiple rows of detectors traversing a plurality of slices of the object at said different axial locations during a single rotation.
In some embodiments of the present invention, said plurality of slices encompass a substantial length of an organ in said object. Also in accordance with the above mentioned aspects, the said plurality of slices may encompass at least the entire length of an organ in said object.
The organ may be, for example a human heart.
In accordance with another aspect of the present invention, the detector arrays comprise multiple rows of individual detectors.
In accordance with some embodiments of the present invention, said detector arrays comprise area detectors. The detectors may be sufficiently large to encompass at least the entire length of an organ in said object, or area detectors that are sufficiently large to encompass a substantial length of an organ in the object.
Optionally, at least one of the said X-ray sources utilizes multiple focal spots.
In some embodiments, said X-ray sources with said associated detector arrays and said object move relative to each other in the Z direction to provide a helical scan. Alternatively, said X-ray sources with said associated detector arrays and said object are moved relative to each other in the Z direction to provide a set of n axial scans where nxe2x89xa71.
According to an aspect of some embodiments of the present invention, the plurality of sources are rotationally removed from each other by any angle xcex8 where 0xc2x0xe2x89xa6xcex8xe2x89xa6180xc2x0.
In an embodiment of the invention, the X-ray sources emit fan beams of X-ray radiation; and the fan beams of at least two of the X-ray sources traverse overlapping sections of the object in the axial direction. Alternatively, the fan beams of at least two of the sources are contiguous to each other in the axial direction. In yet another alternative arrangement, the fan beams of at least two of the sources that illuminate the object are spatially separated in the axial direction. Alternatively, the X-ray beams are cone beams.
According to some embodiments of the present invention, the X-ray detectors are arranged to provide time-coherent multiple slices of the object. Alternatively, the X-ray detector arrays are arranged to provide time-coherent large area views of the patient.
There is further provided, in accordance with an embodiment of the invention a CT system including: a plurality of X-ray sources mounted on a gantry for rotation about an object, a plurality of X-ray detector arrays mounted on said gantry, each being individually associated with and situated opposite to each of the X-ray sources to form a plurality of source-detector units and a source detector unit positioning system for selectively positioning said units at the same axial position or at different axial positions during a single rotation.
There is further provided, in accordance with an embodiment of the invention an imaging method including: mounting a plurality of X-ray sources on a gantry, rotating said gantry around a patient, locating said X-ray sources at said different Z locations, mounting a plurality of detector arrays on said gantry individually associated with and displaced opposite to each of the X-ray sources at different Z locations and simultaneously detecting X-rays that have traversed a plurality of sections of the patient at said different Z locations during a single rotation with said detector arrays.
In accordance with an embodiment of the present invention, said plurality of sections of the patient encompass a substantial length of a human organ, or said plurality of sections of the patient encompass at least the entire length of a human organ and said human organ is an adult heart.
In accordance with an embodiment of the present invention, the detector arrays comprise multiple rows of detectors, where the detectors are individual detectors. Alternatively, the detector arrays comprise wide-area detectors.
According to an embodiment of the present invention, at least one of said X-ray sources utilizes multiple focal spots.
Optionally, a helical scan is provided by moving said X-ray sources with said associated detector arrays and said patient relative to each other in the axial direction.
Alternatively or additionally, moving the X-ray sources with said associated detector arrays and said object relative to each other in the axial direction to provide a set of n axial scans where nxe2x89xa71.
Optionally, the plurality of sources are rotationally removed from each other by any angle xcex8 where 0xc2x0xe2x89xa6xcex8xe2x89xa6180xc2x0. Optionally, the X-ray sources emit fan beams of X-ray radiation and the fan beams of at least two of the X-ray sources traverse overlapping sections of the patient in the axial direction. Alternatively, the fan beams of at least two of the X-ray sources are contiguous to each other in the axial direction. According to still another alternative, the fan beams of at least two of the sources are spatially separated in the axial direction. The fan beams may be cone beams.
An embodiment of the invention includes arranging the X-ray detectors arrays to provide time-coherent multiple slices of the patient. Alternatively, the X-ray detector arrays are arranged to provide time-coherent large area views of the patient.
There is further provided, in accordance with an embodiment of the invention, a CT imaging method is provided that includes mounting a plurality of X-ray sources on a gantry, mounting a plurality of detector arrays on said gantry, each of said detector arrays being individually associated with each of said X-ray sources, and being placed opposite to said sources to form a plurality of source-detector units and selectively locating said units at the same axial location for detecting X-rays that have traversed the same section of a patient during the single rotation during a single rotation or locating said units at different axial locations for simultaneously detecting X-rays that have traversed a plurality of sections of the patient at said different axial locations during a single rotation.